The present invention relates generally to a high-frequency transmitter-receiver apparatus which can be employed as a radar for an automobile or motor vehicle, a communication device in a wireless LAN (local area network) and others. Further, the present invention is concerned with an antenna unit incorporating a high-frequency transmitter-receiver device and a vehicle-onboard radar system incorporating the same.
For the high-frequency transmitter-receiver apparatus employed as the vehicle radar, the wireless LAN or the like, it is important to realize the high-frequency transmitter-receiver apparatus in a miniaturized and simplified structure from the standpoint of mountability and portability of the apparatus.
As one of the conventional high-frequency transmitter-receiver apparatuses designed for use as a radar for a motor vehicle, there can be mentioned the apparatus disclosed in "Proceedings of 1997 IEICE (Institute of Electronics, Information and Communication Engineers) Convention, Paper No. C-2-121: 60 GHz-BAND MILLIMETER-WAVE BAND RADAR UNIT" (hereinafter referred to as the prior art reference 1). In this known transmitter-receiver apparatus, a millimeter-wave (60 GHz band) transmitter-receiver circuit or transceiver circuit is realized as a discrete transmitter-receiver unit encased within a housing. On the other hand, an antenna unit is also realized as a discrete unit and adapted to be connected to the transceiver circuit unit. More specifically, a waveguide terminal serving as input/output terminal for the radio-frequency or RF signal is provided on a rear or bottom surface of the transmitter-receiver unit. Similarly, the antenna unit is equipped with a corresponding waveguide terminal. Thus, the transmitter-receiver unit and the antenna unit can be electrically interconnected by using a waveguide.
Further, in JP-A-8-250913 (hereinafter referred to as the prior art reference 2), there is disclosed a high-frequency transmitter-receiver apparatus in which a planar antenna is formed on an outer surface of a package in which a monolithic microwave integrated circuit (hereinafter referred as MMIC) is hermetically accommodated. FIG. 18 of the accompanying drawings shows a structure of the same. As can be seen in the figure, an antenna 142 is mounted on a bottom surface 141 of the package while a MMIC 143 is mounted as embedded within the package in opposition to the antenna 142. The bottom surface of the MMIC package 143, that is, the top surface of the MMIC package 143 as viewed in the figure, is provided with a slot 146 formed by removing partially a ground conductor layer 145. A conductor pattern 144 constituting a part of a high-frequency circuit and provided on the bottom surface of the MMIC package 143 and the antenna 142 are coupled electromagnetically through the medium of the slot 146. A bonding pad 147 provided on the surface of the MMIC package 143 and a power source terminal 149 also provided on the same surface for receiving external power supply are electrically interconnected by a bonding wire 148.